New York: Rafael Nadal took his US Open first-round record to 13-0 but it was Japanese teenager Naomi Osaka who stole the headlines by knocking out defending champion Angelique Kerber as torrential rains caused more than 50 matches to be shelved on Tuesday.

As players ran for cover from drenched outside courts where just 90 minutes of action was possible, and only three matches completed, Osaka's big-hitting game flourished under the roof of Arthur Ashe Stadium.

The World No 46, born in Japan to a Haitian father and Japanese mother, won 6-3, 6-1 as sixth seed Kerber became the first US Open women's defending champion to lose in the first round since Svetlana Kuznetsova in 2005.

Angelique Kerber, of Germany, reacts after losing a point to Naomi Osaka of Japan in the 1st round of US Open. AP

World No 1 Nadal, meanwhile, began his campaign for a third US Open title with a 7-6 (8/6), 6-2, 6-2 win over Serbia's Dusan Lajovic.

The 31-year-old Spaniard recovered from 3-5 down in the opening set against the 85th-ranked Lajovic, who has never won a match in New York.

"When I was down in the first set, I just tried to be there as he was playing well and controlling the points," said French Open champion Nadal, who is chasing a 16th major.

"But the end of the first set was very important. I got the break back and after that, everything changed."

Osaka, who surrendered a 5-1 final-set lead on the same court in losing to Madison Keys in the third round 12 months ago, fired 22 winners as Kerber went tumbling out of the world's top 10 as well as the tournament.

"At 4-1, I was hoping I don't do what I did last year," said the 19-year-old Osaka, who admitted suffering a brief flashback to her tearful loss to Keys.

Osaka will face either Sweden's Rebecca Peterson or Denisa Allertova of the Czech Republic for a place in the last 32.

"I just want to play good. I did that today and so I want to carry that into the next match," added the Japanese teenager, who secured her first career win over a top-10 player.

'Not the best day'

Kerber is the third top seed to go out in the first round after No 2 Simona Halep and seventh-seeded Johanna Konta lost on Monday.

"She just went for it," said 29-year-old Kerber. "For sure, it was not the best day and not the best match for me."

US Open chiefs decided to cancel 44 singles matches and postpone the completion of 11 others until Wednesday because of the unrelenting rain.

In total, only nine singles matches were due to be completed out of a scheduled 64.

One man certain to finish under the roof on Tuesday night was Roger Federer, whose capture of the Australian Open and Wimbledon titles in 2017 has taken his Slam count to 19.

He is bidding for a record sixth crown in New York.

The 36-year-old Swiss, who missed the 2016 US Open to rest a knee injury, takes on US teenager Frances Tiafoe under the lights, looking to take his first round record to 17-0.

Federer defeated the World No 70 in straight sets in Miami this year but Tiafoe, the son of a Sierra Leone immigrant, illustrated his growing reputation by seeing off World No 6 Alexander Zverev in Cincinnati.

World No 1 Karolina Pliskova, bidding to back her lofty status with a maiden first Grand Slam title, was able to make a winning start, courtesy of playing under the roof on Ashe.

The 25-year-old from Czech Republic, Pliskova, the runner-up in 2016, eased past Poland's Magda Linette 6-2, 6-1 on the back of eight aces and 29 winners.